The process of electrostatographic copying, as originally disclosed by C. F. carlson in U.S. Pat. No. 2,297,691, involves the uniform electrostatic charging of a layer of photoconductive material dispersed on a conductive substrate with subsequent exposure of the charged layer to a light and shadow image to selectively discharge the photoconductive layer and thereby form a latent electrostatic image on the surface of the layer corresponding to the shadow areas. The latent image is developed by contacting the layer with a particulate electroscopic marking material, commonly referred to as toner, which adheres to the non-discharged areas and can be transferred to a receiving member such as paper in imagewise configuration.
The conductive substrate and layer of photoconductive material, which normally contains a resistive barrier layer between the substrate and photoconductive material and may have a protective overcoating on the surface of the photoconductive layer, is generally referred to as the photoreceptor. Typically, the photoconductive material used in photoreceptors is amorphous selenium or an alloy thereof.
Photoreceptors are easily damagaed in field use such as by paper scratching and handling damage which may occur when the photoreceptor is installed or serviced. In addition, foreign matter such as paper clips may come into contact with the photoreceptor during the copying process and gouge the layer of photoconductive material. The damaged photoreceptor is left with depressions on its surface which reduce copy quality. In the case where the depression is deep enough so as to protrude through the photoconductive material to the conductive substrate, the damaged area connot hold a charge and will not contribute to the formation of the latent image. Less severe scratches which do not form depressions through the entire thickness of the photoconductive layer are also problematical. Copy quality can be reduced initially since the photoconductive material remaining in the damaged area may, upon charging and imagewise exposure, have a contrast potential less than the sensitivity of the system. In addition, as the imaging and development cycle is repeated, toner particles tend to build up in the depressions since ordinary photoreceptor cleaning techniques are effective in removing toner only when it is on a relatively smooth surface. The buildup of toner particles, which are normally non-conductive, results in damaged areas retaining their charge during exposure and thereby forming part of the latent image. These areas are developed along with the rest of the latent image and ultimately show up as dark areas when the toner is transferred from the photoreceptor to the paper.
As the photoreceptor receives progressively more scratches, it reaches a point where copy quality is unacceptable whereupon it must be replaced or repaired with the latter option obviously being preferred. One method of repairing selenium based photoreceptors involves buffing the damaged areas to physically remove the depression by abrading away the photoconductive material in the scratched area down to a thickness commensurate with the total layer thickness less the depth of the depression. This repair method works well for shallow scratches, but in situations where the scratch is deep enough to cause a depression up to and greater than half the total thickness of the photoconductive layer, the amount of buffing required becomes burdensome.
Accordingly, it would be desirable and it is an object of the present invention to provide a novel method for the repair of electrostatographic photoreceptors having a layer comprising selenium dispersed on a conductive substrate and having depressions in the selenium layer.
A further object is to provide such a method which is readily adaptable for field use.
An additional object is to provide such a method which is quick, easy to use and can be practiced without special training and/or equipment.